Lithography patterning with flexible solution adjustment

ABSTRACT

A method for lithography patterning includes forming a first layer over a substrate, the first layer being radiation-sensitive, exposing the first layer to a radiation, mixing a first solution and a second solution, thereby forming a developer, and dispensing the developer to the exposed first layer to form a pattern over the substrate. The dispensing of the developer includes varying a concentration of a developing chemical in the developer in multiple stages, such that the concentration of the developing chemical in the developer increases from a first stage to a subsequent second stage, and increases from the second stage to a subsequent third stage real-time during the dispensing.

PRIORITY

This is a continuation of U.S. patent application Ser. No. 16/741,463,filed Jan. 13, 2020, which is a continuation of U.S. patent applicationSer. No. 16/049,208, filed Jul. 30, 2018, which is a divisional of U.S.patent application Ser. No. 15/061,812, filed Mar. 4, 2016, issued U.S.patent Ser. No. 10/386,723, herein incorporated by reference in itsentirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs.

For example, lithography has been the traditional method fortransferring IC patterns to semiconductor wafers. In a typicallithography process, a resist film is coated on a surface of a wafer andis subsequently exposed and developed to form a resist pattern. Theresist pattern is then used for etching the wafer to form an IC. Thequality of the resist pattern directly impacts the quality of the finalIC. The measures of the quality of a resist pattern include criticaldimension variance, line edge roughness (LER), and line width roughness(LWR). As the semiconductor scaling down process continues, it isdesirable to improve the existing developing processes and systems so asto reduce critical dimension variance, LER, and LWR of the resistpatterns to meet pre-determined critical dimension uniformity (CDU).

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 illustrates a flow chart of a lithography patterning methodaccording to various aspects of the present disclosure.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, and 2I illustrate cross sectionalviews of forming a target pattern according to the method of FIG. 1 , inaccordance with an embodiment.

FIG. 3 illustrates a flow chart of a resist developing process withflexible solution adjustment, in accordance with some embodiments.

FIGS. 4A and 4B each show a graph of a flexible solution adjustment in aresist developing process, constructed according to aspects of thepresent disclosure in one or more embodiments.

FIG. 5A is a schematic view of a lithography developing apparatusconstructed according to aspects of the present disclosure in one ormore embodiments.

FIGS. 5B and 5C are schematic views of a part of the lithographydeveloping apparatus of FIG. 5A, in accordance with some embodiments.

FIG. 5D illustrates a flow chart of a flexible developer concentrationadjustment method, according to various aspects of the presentdisclosure.

FIG. 6 shows a graph of a flexible solution adjustment in a resisttreatment process, constructed according to aspects of the presentdisclosure in one or more embodiments.

FIG. 7A is a schematic view of a pattern treatment apparatus constructedaccording to aspects of the present disclosure in one or moreembodiments.

FIG. 7B illustrates a flow chart of a flexible treatment chemicaladjustment method using the apparatus of FIG. 7A, according to variousaspects of the present disclosure.

FIG. 8A is a schematic view of another pattern treatment apparatusconstructed according to aspects of the present disclosure in one ormore embodiments.

FIG. 8B illustrates a flow chart of a flexible treatment chemicaladjustment method using the apparatus of FIG. 8A, according to variousaspects of the present disclosure.

FIG. 9 is a schematic view of a lithography developing systemconstructed according to aspects of the present disclosure in one ormore embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The present disclosure in various embodiments is generally related tomethods for semiconductor device fabrication, and more particularly tomethods of lithography patterning. In lithography patterning, after aresist film is exposed, it is developed in a developer. The developerremoves portions of the resist film, thereby forming a resist patternwhich may include line patterns and/or trench patterns. The resistpattern may undergo additional rinsing and treatment processes to befurther solidified. The resist pattern is used as an etch mask insubsequent etching processes, transferring the pattern to underlyingpatterning layers. The lines and/or trenches of a resist pattern usuallyexhibit non-uniform critical dimensions (CD) across a substrate (e.g., awafer) due to various factors. Such CD non-uniformity in a resistpattern may lead to manufacturing defects and should be avoided wheneverpossible. This is particularly true in nanometer (nm) fabricationregimes. The present disclosure provides methods and systems fordeveloping resist patterns with improved CD uniformity.

FIG. 1 is a flow chart of a method 100 of patterning a substrate (e.g.,a semiconductor wafer) according to various aspects of the presentdisclosure. The method 100 may be implemented, in whole or in part, by asystem employing deep ultraviolet (DUV) lithography, extreme ultraviolet(EUV) lithography, electron beam (e-beam) lithography, x-raylithography, and other appropriate lithography processes to improvepattern dimension accuracy. Additional operations can be providedbefore, during, and after the method 100, and some operations describedcan be replaced, eliminated, or relocated for additional embodiments ofthe method. The method 100 is an example, and is not intended to limitthe present disclosure beyond what is explicitly recited in the claims.The method 100 is described below in conjunction with FIGS. 2A-2Iwherein a semiconductor device 200 is fabricated by using embodiments ofthe method 100. The semiconductor device 200 may be an intermediatedevice fabricated during processing of an IC, or a portion thereof, thatmay comprise SRAM and/or other logic circuits, passive components suchas resistors, capacitors, and inductors, and active components such asp-type FETs (PFETs), n-type FETs (NFETs), fin-like FETs (FinFETs), otherthree-dimensional (3D) FETs, metal-oxide semiconductor field effecttransistors (MOSFET), complementary metal-oxide semiconductor (CMOS)transistors, bipolar transistors, high voltage transistors, highfrequency transistors, other memory cells, and combinations thereof.

The method 100 (FIG. 1 ) is provided with a substrate 202 (FIG. 2A) atoperation 102. Referring to FIG. 2A, the substrate 202 includes one ormore layers of material or composition. In an embodiment, the substrate202 is a semiconductor substrate (e.g., wafer). In another embodiment,the substrate 202 includes silicon in a crystalline structure. Inalternative embodiments, the substrate 202 includes other elementarysemiconductors such as germanium; a compound semiconductor such assilicon carbide, gallium arsenide, indium arsenide, and indiumphosphide; an alloy semiconductor such as GaAsP, AlInAs, AlGaAs, InGaAs,GaInP, and/or GaInAsP; or combinations thereof. The substrate 202 mayinclude a silicon on insulator (SOI) substrate, be strained/stressed forperformance enhancement, include epitaxial regions, include isolationregions, include doped regions, include one or more semiconductordevices or portions thereof, include conductive and/or non-conductivelayers, and/or include other suitable features and layers. In thepresent embodiment, the substrate 202 includes a patterning layer 204.In an embodiment, the patterning layer 204 is a hard mask layerincluding material(s) such as amorphous silicon (a-Si), silicon oxide,silicon nitride (SiN), titanium nitride, or other suitable material orcomposition. In an embodiment, the patterning layer 204 is ananti-reflection coating (ARC) layer such as a nitrogen-freeanti-reflection coating (NFARC) layer including material(s) such assilicon oxide, silicon oxygen carbide, or plasma enhanced chemical vapordeposited silicon oxide. In various embodiments, the patterning layer204 may include a high-k dielectric layer, a gate layer, a hard masklayer, an interfacial layer, a capping layer, a diffusion/barrier layer,a dielectric layer, a conductive layer, other suitable layers, and/orcombinations thereof. In another embodiment, the substrate 202 is a masksubstrate that may include a low thermal expansion material such asquartz, silicon, silicon carbide, or silicon oxide-titanium oxidecompound. To further this example, the substrate 202 may be a masksubstrate for making a deep ultraviolet (DUV) mask, an extremeultraviolet (EUV) mask, or other types of masks.

The method 100 (FIG. 1 ) proceeds to operations 104 by forming a layer206 over the substrate 202 (FIG. 2B). The layer 206 includes aradiation-sensitive material. Referring to FIG. 2B, in an embodiment,the layer 206 is formed by spin-on coating a liquid polymeric materialonto the substrate 202, followed by a soft baking process and a hardbaking process. In an embodiment, the layer 206 is a photoresist such asan I-line resist, a DUV resist including a krypton fluoride (KrF) resistand argon fluoride (ArF) resist, a EUV resist, an electron beam (e-beam)resist, and an ion beam resist. For convenience, the layer 206 is simplyreferred to as the resist 206 in the following discussion. In variousembodiments, the resist 206 may be a positive resist or a negativeresist. A positive resist is generally insoluble in a developer, butbecomes soluble upon radiation. A negative resist has the oppositebehavior: it is generally soluble in a developer, but becomes insolubleupon radiation.

The method 100 (FIG. 1 ) proceeds to operation 106 by exposing theresist 206 to a radiation 208 in a lithography system. Referring to FIG.2C, the radiation 208 may be an I-line (365 nm), a DUV radiation such asKrF excimer laser (248 nm) or ArF excimer laser (193 nm), a EUVradiation (e.g., 13.8 nm), an e-beam, an x-ray, an ion beam, or othersuitable radiations. Operation 106 may be performed in air, in a liquid(immersion lithography), or in a vacuum (e.g., for EUV lithography ande-beam lithography). In an embodiment, the radiation 208 is patternedwith a mask (not shown), such as a transmissive mask or a reflectivemask, which may include resolution enhancement techniques such asphase-shifting and/or optical proximity correction (OPC). In anotherembodiment, the radiation 208 is directly modulated with a predefinedpattern, such as an IC layout, without using a mask (masklesslithography). In the present embodiment, the radiation 208 exposesportions 206A of the resist 206 according to a pattern 209, either witha mask or maskless. In the present embodiment, the resist 206 is apositive resist and the irradiated portions 206A become soluble in adeveloper. In an alternative embodiment, the resist 206 is a negativeresist and the irradiated portions 206A become insoluble in a developer.The semiconductor device 200 may be subjected to additional processes,such as a post-exposure baking process.

The method 100 (FIG. 1 ) proceeds to operation 108 by developing theexposed resist 206 with a flexible solution adjustment process,constructed according to various aspects of the present disclosure. Inan embodiment, the operation 108 includes one or more processes such asdeveloping (FIG. 2D), rinsing (FIG. 2E), and treatment processes (FIGS.2F and 2G), which will be further discussed below. The irradiatedportions 206A are removed in the operation 108, resulting in a resistpattern 206B (FIG. 2H). In the example as shown in FIG. 2H, the resistpattern 206B is represented by a line pattern. However, the followingdiscussion is equally applicable to resist patterns represented bytrenches. At operation 110, the method 100 transfers the pattern fromthe resist pattern 206B to the substrate 202, which will be furtherdiscussed below.

As discussed above, the quality of the resist pattern 206B directlyimpacts the quality of the final fabricated IC. Among various measuresof the quality of the resist pattern 206B is the critical dimensionvariance, e.g., a 3σ deviation of a minimum pattern dimension. Othermeasures include line width roughness (LWR) and/or line edge roughness(LER). Some developing processes may lead to non-uniform CDs across awafer. For example, CDs in or near the center of a wafer may be largerthan the CDs in outer areas of the wafer. In one example with a 300-nmwafer, the CDs of a EUV resist pattern could vary in excess of 3 nm fromthe center of the wafer to its perimeter in some instances. Suchexcessive CD variance may be unacceptable to certain production lines.The inventor of the present disclosure observed that one factor leadingto such excessive CD variance is how the developer 210's chemicalconcentration is controlled during the developing of the resist 206. Ina typical developing process, a developer's chemical concentrationremains about constant throughout the developing process. The developeris dispensed at the center of a wafer and flows to the rest areas of thewafer due to centrifugal force generated by spinning of the wafer. As aresult, not all areas of the wafer receive the same amount of thedeveloper and the center of the wafer is over-developed compared to theouter areas of the wafer. The present disclosure addresses such issueswith a flexible solution adjustment scheme where the chemicalconcentration of the developer 210 is flexibly adjusted as a function oftime. In one example, the developer 210 starts with a low chemicalconcentration. As it flows and fills the entire area of a wafer, itschemical concentration is increased to achieve certain chemicalperformance. As a result, the entire wafer is developed more evenly,providing better CDU than the typical developing processes. Anembodiment of the flexible solution adjustment is shown in FIG. 3 .

Referring to FIG. 3 , shown therein is an embodiment of the operation108, implemented with a flexible solution adjustment scheme according tovarious aspects of the present disclosure. The operation 108 will bediscussed collectively with FIGS. 2D-2G. In a brief overview, theoperation 108 includes steps 132, 134, 136, and 138. In the step 132,the operation 108 flexibly adjusts a chemical concentration (i.e., as afunction of time) in a developer 210 while developing the resist 206(FIG. 2D) with the developer 210. In the step 134, the operation 108rinses the resist pattern 206B with a rinse solution 212 (FIG. 2E). Inthe step 136, the operation 108 flexibly adjusts a chemicalconcentration in a first treatment chemical 214 while treating theresist pattern 206B (FIG. 2F) with the chemical 214. In the step 138,the operation 108 flexibly adjusts a chemical concentration in a secondtreatment chemical 216 while treating the resist pattern 206B (FIG. 2G)with the chemical 216. Additional operations can be provided before,during, and after the steps 132-138, and some operations described canbe replaced, eliminated, modified, or moved around for additionalembodiments of the method. For example, an embodiment of the operation108 may flexibly adjust the developer 210 in the step 132, but keep thetreatment chemicals 214 and/or 216 constant (without flexibleadjustment) in the steps 136 and/or 138 respectively. For anotherexample, an embodiment of the operation 108 may include another rinsestep (similar to the step 134) between the treatment steps 136 and 138.One of ordinary skill in the art may recognize other examples ofsemiconductor fabrication processes that may benefit from aspects of thepresent disclosure.

At the step 132, the operation 108 applies the developer 210 to theexposed resist 206 (FIG. 2D). The developer 210 includes a developingchemical dissolved in a solvent. In one example, the developer 210 is apositive tone developer, e.g., containing tetramethylammonium hydroxide(TMAH) dissolved in an aqueous solution. In another example, thedeveloper 210 is a negative tone developer, e.g., containing n-ButylAcetate (nBA) dissolved in an organic solvent. A concentration of thedeveloping chemical (e.g., TMAH or nBA) in the developer 210 (or simply“developer concentration”) is flexibly adjusted during the developingprocess as a function of time. In an embodiment, the developer 210starts with a first developer concentration. After the resist 206 hasbeen developed for a first duration, the developer 210 is changed tohave a second developer concentration that is different from the firstdeveloper concentration, and the resist 206 is developed for a secondduration. In an embodiment, the first developer concentration is lowerthan the second developer concentration, making the step 132 a “dilutedeveloping” process. Further adjustments of the developer concentrationmay follow after the second duration, until the resist 206 is fullydeveloped.

A graph 410 in FIG. 4A illustrates that the concentration of thedeveloping chemical in the developer 210 is a function of time (i.e., itis not constant, and it may vary over time or during some periods oftime) during the step 132, in accordance with an embodiment. Referringto FIG. 4A, the step 132 includes a 6-stage flexible adjustment in theillustrated embodiment. The six stages are labeled as c₁, c₂, c₃, c₄,c₅, and c₆, which are also the values of the developer concentration atthe respective stages. Within each stage, the developer concentrationremains substantially constant. From one stage to a subsequent (theimmediately next) stage, the developer concentration varies. The sixconcentrations c₁, c₂, c₃, c₄, c₅, and c₆ may be all different, or someof them may be the same. For example, in an embodiment, it may hold truethat c₂≠c₃ and c₃≠c₄, but c₂=c₄. Further, the graph 410 shown in FIG. 4Ais merely an example of the flexible adjustment of the developer 210.The various developer concentrations and developing durations may bemodified and/or removed, and additional developer concentrations anddeveloping durations may be added or inserted for additionalembodiments. For example, one or more of the steps, c₂, c₃, c₄, and c₅,may have duration of zero, which makes the concentration of thedeveloping chemical in the developer 210 varies more continuously thanhaving steps.

Still referring to FIG. 4A, initially, the developer 210 has aconcentration c₁, which may be low, for example, near 0.0%. The resist206 may not be actually developed in this initial stage. At time t₁, theconcentration of the developing chemical in the developer 210 starts toincrease linearly and reaches c₂ at time t₂. The developer concentrationremains substantially the same from t₂ to t₃. At time t₃, the developerconcentration starts to increase linearly and reaches c₃ at time t₄. Therates of increase (e.g., % per second) from c₁ to c₂ and from c₂ to c₃may be the same or different. The developer concentration remainssubstantially the same from t₄ to t₅. Afterwards, the developerconcentration starts to decrease at t₅ linearly and reaches c₄ at timet₆. Similarly, the developer concentration decreases from t₇ to t₈ andfrom t₉ to t₁₀. The rates of decrease (e.g., % per second) in the threeperiods (t₅-t₆, t₇-t₈, and t₉-t₁₀) may be the same or different. Thedeveloper concentration remains substantially the same during theperiods t₆-t₇, t₈-t₉, and after t₁₀, respectively. The developer 210 isbeing applied to the resist 206 while its concentration is beingadjusted according to the graph 410.

A graph 420 in FIG. 4B illustrates an embodiment of the flexibleadjustment of the developer 210 which includes TMAH in an aqueoussolution. Referring to FIG. 4B, the developer 210 has an initial TMAHconcentration near 0.0%. From Time=5 seconds to Time=6 seconds, the TMAHconcentration increases from 0.0% to about 1.2%. The resist 206 isdeveloped with 1.2% TMAH for about 6 seconds. Then, from Time=11 secondsto Time=12 seconds, the TMAH concentration increases from about 1.2% toabout 2.38%. The resist 206 is further developed with 2.38% TMAH forabout 2 seconds. It is noted that the resist 206 is also being developedwhile the TMAH concentration is being changed (e.g., during the timeperiods from Time=5 seconds to Time=6 seconds and from Time=10 secondsto Time=11 seconds). Further adjustments follow, which includedecreasing of the TMAH concentration from 2.38% to 1.2% (from Time=14seconds to Time=15 seconds, and from Time=24 seconds to Time=25seconds), increasing of the TMAH concentration from 1.2% to 2.38%(Time=19 seconds to Time=20 seconds), and decreasing of the TMAHconcentration from 1.2% to near 0.0% (from Time=29 seconds to Time=30seconds). After Time=30 seconds, the resist 206 has been fullydeveloped, with the irradiated portions 206A dissolved by the developer210. The step 134 (FIG. 3 ) may follow, e.g., at Time=36 seconds, toremove any residue, including excessive developer 210, from the device200.

The step 132 (FIG. 3 ) may be implemented in a developing system 500, anembodiment of which is shown in FIG. 5A. Referring to FIG. 5A, thesystem 500 includes a substrate stage 502 designed to retain asubstrate, such as the substrate 202. As shown, the substrate 202 isfurther coated with the resist 206 which has been exposed and is readyto be developed. The substrate stage 502 includes a mechanism, such asvacuum suction mechanism, e-chucking, or other suitable mechanism, tosecure the substrate 202. The system 500 further includes a motionmechanism 504 integrated with the substrate stage 502 and is operable todrive the substrate stage 502 and the substrate 202 secured thereon invarious motion modes. In some embodiments, the motion mechanism 504includes a motor to drive the substrate stage 502 and the substrate 202to spin at a certain spin speed during various operations (such asdeveloping and rinsing). In some embodiments, the motion mechanism 504includes an elevation module to move the substrate 202 along a verticaldirection so that the substrate 202 is able to be positioned at a loweror higher level.

The system 500 further includes a sub-system 505 which applies thedeveloper 210 to the resist 206. The sub-system 505 includes a storageand mixer (or mixer) 506, a supply pipe 508, and a supply nozzle 510coupled together. The supply nozzle 510 is movably positioned directlyabove the center of the substrate 202. The developer 210 is dispensedthrough the supply nozzle 510 over the substrate 202 while it is spun.After the developer 210 is dispensed onto the resist 206 at the centerof the substrate 202, it flows to other parts of the resist 206 due to acentrifugal force generated by the spin. The system 500 further includesa cup 512 and a drain (or exhaust) 514. The cup 512 is configured aroundthe substrate stage 502 to effectively catch the developer 210 (and theresist portions 206A dissolved therein) spun off from the substrate 202during the developing process. In some embodiments, the cup 512 isdesigned to have a cylindrical structure. The cup 512 is integrated withthe drain 514 such that the liquid received from the cup 512 is sent outthrough the drain 514 for further processing.

In the present embodiment, the developer 210 is obtained by real-timemixing two solutions, a first solution 210A and a second solution 210B,in the mixer 506. In an embodiment, the first solution 210A contains adeveloping chemical (e.g., TMAH or nBA) at a first concentration, thesecond solution 210B contains the developing chemical at a secondconcentration that is lower than the first concentration, and thedeveloper 210 contains the developing chemical in a range from about thesecond concentration to about the first concentration, flexiblyadjusted. In a further embodiment, the second solution 210B is free ofthe developing chemical and the developer 210 contains the developingchemical in a range from about 0.0% to about the first concentration,flexibly adjusted. For example, the first solution 210A may contain TMAHat 2.38%, the second solution 210B may contain deionized water (DIW)free of TMAH, and the developer 210 may contain TMAH in a range fromabout 0.0% to about 2.38%, flexibly adjusted, as will be discussedbelow.

Still referring to FIG. 5A, the mixer 506 includes a first container516A which stores the first solution 210A, and a second container 516Bwhich stores the second solution 210B. The mixer 506 further includespumping mechanisms (such as pressure pumps or pressurized gases) 518Aand 518B to force the solutions 210A and 210B into supply pipes 520A and520B, respectively. The mixer 506 further includes control units 522Aand 522B coupled to the supply pipes 520A and 520B, respectively. Thesupply pipe 508 is coupled to the supply pipes 520A and 520B at thedownstream of the control units 522A and 522B for receiving thesolutions 210A and 210B, respectively. The control unit 522A isconfigured to control a flow rate 523A of the solution 210A going intothe supply pipe 508. The control unit 522B is configured to control aflow rate 523B of the solution 210B going into the supply pipe 508. Oneor both of the control units 522A and 522B are configured to provide atleast three levels of flow rate control: a minimum flow rate, a maximumflow rate, and an intermediate flow rate that is less than the maximumflow rate and greater than the minimum flow rate. In some embodiments,the control units 522A and 522B may be integrated with the pumpingmechanisms 518A and 518B respectively. The two solutions, 210A and 210B,mix in the supply pipe 508 in a section proximal to the supply pipes520A and 520B (e.g., in a section enclosed by a dotted box 524) to formthe developer 210. The supply pipes 520A, 520B, and 508 may form a“T-shaped” connection as shown in FIG. 5A. Alternatively, the supplypipes 520A, 520B, and 508 may form a “Y-shaped” connection as shown inFIG. 5B. In a further embodiment as shown in FIG. 5C, the supply pipe508 includes a proximal section 508A (closer to the supply pipes 520Aand 520B) that is larger in diameter than a distal section of the supplypipe 508 (further away from the supply pipes 520A and 520B, such as nearthe supply nozzle 510). The section 508A may serve as a small tank thattemporarily stores the solutions 210A and 210B so that they mixuniformly before being dispensed over the resist 206.

With the mixer 506, the developer 210's concentration can be flexiblyadjusted during the developing process. In an embodiment, the controlunits 522A and 522B are configured to control the flow rates of thesolutions 210A and 210B according to a process recipe so as to produce adesired developer concentration profile as a function of time, such asillustrated in FIGS. 4A and 4B. An embodiment of the step 132 (alsoreferred to as the method 132) is shown in FIG. 5D, which is brieflydescribed below in conjunction with the sub-system 500. The method 132includes an operation 152A which supplies a first solution (e.g.,solution 210A) to a supply pipe (e.g., supply pipe 508) at a first flowrate (e.g., flow rate 523A). The method 132 further includes anoperation 154A which supplies a second solution (e.g., solution 210B) tothe supply pipe at a second flow rate (e.g., flow rate 523B). The firstand second solutions are supplied to the supply pipe simultaneously andmix into a developer (e.g., developer 210) in the supply pipe. Themethod 132 further includes an operation 156A which applies thedeveloper from the supply pipe to a target (e.g., the exposed resist206). The method 132 further includes an operation 158A which adjustsone or both of the first and second flow rates to vary a concentrationof a developing chemical in the developer.

In an embodiment, the first solution 210A is a positive tone developer,such as an aqueous solution containing 2.38% TMAH; and the secondsolution 210B is deionized water (DIW). To further this embodiment, thefirst and second solutions, 210A and 210B, may be flexibly mixed in themixer 506 to form the developer 210 so as to have a TMAH concentrationranging from about 0.0% to about 2.38%. In another embodiment, the firstsolution 210A is a negative tone developer, such as a solutioncontaining 95% nBA; and the second solution 210B is an organic solventsuch as the solvent OK73 (containing 70% by weight Propylene glycolmonomethylether (PGME) and 30% by weight Propylene glycolmonomethylether acetate (PGMEA)). To further this embodiment, the firstand second solutions, 210A and 210B, may be flexibly mixed in the mixer506 to form the developer 210 so as to have an nBA concentration rangingfrom about 90% to about 95%.

Referring back to FIG. 3 , after the resist 206 has been developed, theoperation 108 rinses the pattern 206B with the rinse solution 212 (FIG.2E) in the step 134. In an embodiment, the rinse solution 212 containswater, such as DIW. In an alternative embodiment, the rinse solution maycontain a surfactant dissolved in water. The rinse solution 212 is usedto remove or displace residual developer 210 (and any dissolved resist206A therein) from the device 200. In an embodiment, the rinse solution212 is dispensed through a rinse supply nozzle different from the supplynozzle that dispenses the developer 210. In an alternative embodiment,with the system 500 shown in FIG. 5A, the rinse solution 212 may bedispensed through the same nozzle 510 that dispenses the developer 210.For example, the control unit 522A may shut off the flow of the firstsolution 210A that contains the developing chemical, and only the secondsolution 210B, which comprises DIW, is sent to the supply nozzle 510. Inthis way, the system 500 can be used for multiple developing steps(e.g., the steps 132 and 134), simplifying the operations and reducingsystem costs.

Still referring to FIG. 3 , after the pattern 206B has been rinsed, theoperation 108 treats the pattern 206B with one or more treatmentchemicals to reduce pattern collapse and pattern deformities, such asline edge roughness and line width roughness. In the present embodiment,the operation 108 treats the pattern 206B with two treatment chemicals,the first treatment chemical 214 (FIG. 2F) in the step 136 and thesecond treatment chemical 216 (FIG. 2G) in the step 138. Person havingordinary skill in the art should recognize that the operation 108 mayapply one treatment chemical or more than two treatment chemicals invarious embodiments. The steps 136 and 138 are collectively discussedbelow.

In the present embodiment, the treatment chemicals 214 and 216 includedifferent compositions. Each of the treatment chemicals 214 and 216includes a surfactant. For example, the surfactant may include anaqueous solution containing a polyethylene glycol-based or acetyleneglycol-based surfactant. As another example, each of the treatmentchemicals 214 and 216 includes one or more surfactant solutions selectedfrom the FIRM™ (Finishing up by Improved Rinse Material) family ofsurfactants (e.g., FIRM™-A, FIRM™-B, FIRM™-C, FIRM™-D, FIRM™ Extreme 10,etc.) co-developed by Tokyo Electron Limited (TEL) and Clariant (Japan)KK (Bunkyo-Ku, Tokyo, Japan) (a subsidiary of Swiss manufacturerClariant).

In an embodiment, the treatment chemicals 214 and 216 each undergo arespective surfactant concentration adjustment process before beingapplied to the resist pattern 206B. The adjustment process issubstantially similar to what has been discussed with respect to thestep 132. Hence, it is only briefly described below. In an embodiment,the treatment chemical (214 or 216) may be applied in multiple stages.Within each stage, the surfactant concentration in the treatmentchemical remains substantially constant. From one stage to a subsequentstage, the surfactant concentration in the treatment chemical eitherincreases or decreases. In one particular embodiment, the step 136 (or138) starts with a lower surfactant concentration in the treatmentchemical 214 (or 216). After a first duration, the surfactantconcentration in the treatment chemical 214 (or 216) increases and theresist pattern 206B is rinsed for a second duration. Thereafter,additional treatment stages may follow. In another embodiment as shownin FIG. 6 , the step 136 (or 138) starts with a higher surfactantconcentration in the treatment chemical 214 (or 216) which reaches about100% in less than 2 seconds. After a first duration which is about 3 to4 seconds, the surfactant concentration in the treatment chemical 214(or 216) decreases in a linear step curve until it reaches auser-specified concentration level, which is about 50% in theillustrated example. The linear step curve includes one or more steps.In the illustrated example, there are two steps: a 2-second duration atabout 80% and a 1-second duration at about 60%. The surfactantconcentration remains at the user-specified concentration level for themajority of the treatment cycle, and increases to the full concentrationlevel (near 100%) at the end of the treatment (at about the 33 second).After a short treatment with the high concentration of the surfactant,the treatment chemical is switched off and the DI water is switched on.Various other examples of the flexible adjustment process may beimplemented for each of the steps 136 and 138.

In an embodiment, the developing system 500 includes a sub-system 525(FIG. 7A) which supplies the treatment chemical 214 using a flexibleadjustment scheme, according to various aspects of the presentdisclosure. In another embodiment, the developing system 500 includes asub-system 545 (FIG. 8A) which supplies the treatment chemical 216 usinga flexible adjustment scheme, according to various aspects of thepresent disclosure. The sub-systems 525 and 545 are structurally similarto the sub-system 505 (FIG. 5A). Hence, they are only briefly describedbelow.

Referring to FIG. 7A, the sub-system 525 includes a mixer 526, a supplypipe 528, and a supply nozzle 530 coupled together. The mixer 526includes a container 536A storing a solution 214A, and a container 536Bstoring a solution 214B. In an embodiment, the solution 214A contains asurfactant, and the solution 214B is DIW. The mixer 526 further includespumping mechanisms 538A and 538B to force the solutions 214A and 214Binto supply pipes 540A and 540B, respectively. The mixer 526 furtherincludes control units 542A and 542B coupled to the supply pipes 540Aand 540B, respectively. The supply pipe 528 is coupled to the supplypipes 540A and 540B at the downstream of the control units 542A and 542Bfor receiving the solutions 214A and 214B, respectively. The controlunit 542A determines a flow rate 543A of the solution 214A going intothe supply pipe 528. The control unit 542B determines a flow rate 543Bof the solution 214B going into the supply pipe 528. The solutions 214Aand 214B mix in the supply pipe 528 to form the treatment chemical 214which is dispensed through the supply nozzle 530 onto the resist pattern206B.

FIG. 7B shows an embodiment of the step 136 implemented with the system500 shown in FIG. 7A. Referring to FIG. 7B, the step 136 includes anoperation 152B which supplies the solution 214A to the supply pipe 528at the flow rate 543A. The step 136 further includes an operation 154Bwhich supplies the solution 214B to the supply pipe 528 at the flow rate543B. The solutions 214A and 214B are supplied to the supply pipe 528simultaneously and mix into the treatment chemical 214 in the supplypipe 528. The step 136 further includes an operation 156B which appliesthe treatment chemical 214 from the supply pipe to the resist pattern206B. The step 136 further includes an operation 158B which adjusts oneor both of the flow rates, 543A and 543B, to vary a concentration of asurfactant in the treatment chemical 214.

Referring to FIG. 8A, the sub-system 545 includes a mixer 546, a supplypipe 548, and a supply nozzle 550 coupled together. The mixer 546includes a container 556A storing a solution 216A, and a container 556Bstoring a solution 216B. In an embodiment, the solution 216A contains asurfactant, and the solution 216B is DIW. The solution 216A may have adifferent composition than the solution 214A (FIG. 7A). The mixer 546further includes pumping mechanisms 558A and 558B to force the solutions216A and 216B into supply pipes 560A and 560B, respectively. The mixer546 further includes control units 562A and 562B coupled to the supplypipes 560A and 560B, respectively. The supply pipe 548 is coupled to thesupply pipes 560A and 560B at the downstream of the control units 562Aand 562B for receiving the solutions 216A and 216B, respectively. Thecontrol unit 562A determines a flow rate 563A of the solution 216A goinginto the supply pipe 548. The control unit 562B determines a flow rate563B of the solution 216B going into the supply pipe 548. The solutions216A and 216B mix in the supply pipe 548 to form the treatment chemical216 which is dispensed through the supply nozzle 550 onto the resistpattern 206B.

FIG. 8B shows an embodiment of the step 138 implemented with the system500 shown in FIG. 8A. Referring to FIG. 8B, the step 136 includes anoperation 152C which supplies the solution 216A to the supply pipe 548at the flow rate 563A. The step 138 further includes an operation 154Cwhich supplies the solution 216B to the supply pipe 548 at the flow rate563B. The solutions 216A and 216B are supplied to the supply pipe 548simultaneously and mix into the treatment chemical 216 in the supplypipe 548. The step 138 further includes an operation 156C which appliesthe treatment chemical 216 from the supply pipe 548 to the resistpattern 206B. The step 138 further includes an operation 158C whichadjusts one or both of the flow rates, 563A and 563B, to vary aconcentration of a surfactant in the treatment chemical 216.

FIG. 9 shows an embodiment of the developing system 500. Referring toFIG. 9 , the system 500 includes the sub-systems 505, 525, and 545 whichhave been discussed with reference to FIGS. 5A, 7A, and 8A respectively.The system 500 further includes a sub-system 565 which is configured tosupply DIW from a storage unit 566 through a supply pipe 568 to a supplynozzle 570. In an embodiment, the sub-system 565 is used during therinsing operation in the step 134 (FIG. 3 ). In various embodiments,each of the supply nozzles 510, 530, 550, and 570 is independentlymovable and can be positioned directly above a wafer (not shown) securedon the substrate stage 502 during the various developing operationsdiscussed above.

Referring to FIG. 1 , after the resist pattern 206B has been developed.The method 100 proceeds to operation 110 to etch the substrate 202 usingthe resist pattern 206B as an etch mask, thereby transferring thepattern to the substrate 202 (FIG. 2I). In an embodiment, the patterninglayer 204 is a hard mask layer. To further this embodiment, the patternis first transferred from the resist pattern 206B to the hard mask layer204, then to other layers of the substrate 202. For example, the hardmask layer 204 may be etched using a dry (plasma) etching, a wetetching, and/or other etching methods. The resist pattern 206B may bepartially or completely consumed during the etching of the hard masklayer 204. In an embodiment, any remaining portion of the resist pattern206B may be stripped off, leaving a patterned hard mask layer 204 overthe substrate 202, as illustrated in FIG. 2I.

Although not shown in FIG. 1 , the method 100 may proceed to forming afinal pattern or an IC device on the substrate 202. In a non-limitingexample, the substrate 202 is a semiconductor substrate and the method100 proceeds to forming fin field effect transistor (FinFET) structures.In this embodiment, operation 110 forms a plurality of active fins inthe semiconductor substrate 202. The active fins have uniform CD, thanksto the extreme low CDU of the resist pattern 206B.

Although not intended to be limiting, one or more embodiments of thepresent disclosure provide many benefits to lithography processes andthe ICs thereby produced. For example, embodiments of the presentdisclosure are capable of producing a developer (or a treatmentchemical) with its concentration varied as a function of time during thedeveloping (or treatment) process. In a particular embodiment, thedeveloper (or the treatment chemical) may begin with a lowerconcentration and gradually increases its concentration as it isdistributed over an entire area of a wafer. This greatly improvescritical dimension uniformity across the entire area of the wafer. Inaddition, embodiments of the present disclosure enable flexiblelithography system designs and reduce system costs.

In one exemplary aspect, the present disclosure is directed to a methodfor lithography patterning. The method includes forming a first layerover a substrate, the first layer being radiation-sensitive. The methodfurther includes exposing the first layer to a radiation. The methodfurther includes applying a developer to the exposed first layer,resulting in a pattern over the substrate, wherein the developerincludes a developing chemical and a concentration of the developingchemical in the developer is a function of time during the applying ofthe developer.

In another exemplary aspect, the present disclosure is directed to amethod for lithography patterning. The method includes providing asubstrate, and forming a first layer over the substrate, the first layerbeing radiation-sensitive. The method further includes exposing thefirst layer to a radiation. The method further includes applying adeveloper onto the exposed first layer to result in a pattern over thesubstrate, wherein the developer includes a developing chemical. Duringthe applying of the developer, the method further includes adjusting aconcentration of the developing chemical in the developer.

In another exemplary aspect, the present disclosure is directed to amethod for lithography patterning. The method includes forming a firstlayer over a substrate, the first layer being radiation-sensitive; andexposing the first layer to a radiation. The method further includesapplying a first developer to the exposed first layer, wherein the firstdeveloper includes a first chemical at a first concentration. After theapplying of the first developer, the method further includes applying asecond developer to the exposed first layer, wherein the seconddeveloper includes the first chemical at a second concentration that isdifferent from the first concentration. In an embodiment, the applyingof the first developer includes dispensing the first developer to theexposed first layer through a supply nozzle; and the applying of thesecond developer includes dispensing the second developer to the exposedfirst layer through the supply nozzle. In a further embodiment, afterthe applying of the first and second developers, the method furtherincludes applying a third developer to the exposed first layer, whereinthe third developer includes the first chemical at a third concentrationand is dispensed to the exposed first layer through the supply nozzle.

In another exemplary aspect, the present disclosure is directed to amethod for lithography patterning. The method includes forming a firstlayer over a substrate, the first layer being radiation-sensitive;exposing the first layer to a radiation; developing the exposed firstlayer in a developer, resulting in a developed first layer; and rinsingthe developed first layer with a rinse solution. After the rinsing ofthe developed first layer, the method further includes treating thedeveloped first layer with a first chemical, wherein the first chemicalincludes a first surfactant and a concentration of the first surfactantin the first chemical is a function of time during the treating of thedeveloped first layer with the first chemical. In an embodiment, afterthe treating of the developed first layer with the first chemical, themethod further includes treating the developed first layer with a secondchemical. The second chemical includes a second surfactant. Aconcentration of the second surfactant in the second chemical is afunction of time during the treating of the developed first layer withthe second chemical. The first and second surfactants have differentcompositions. In an embodiment, the treating of the developed firstlayer with the first chemical includes supplying deionized water (DIW)into a supply pipe at a first flow rate; supplying a solution containingthe first surfactant into the supply pipe at a second flow rate, whereinthe DIW and the solution are mixed in the supply pipe to form the firstchemical; dispensing the first chemical onto the developed first layer;and adjusting at least one of: the first flow rate and the second flowrate so as to vary the concentration of the first surfactant in thefirst chemical.

In another exemplary aspect, the present disclosure is directed to asystem for lithography patterning. The system includes a first supplypipe for supplying a first solution, a second supply pipe for supplyinga second solution, and a third supply pipe coupled to the first andsecond supply pipes for receiving the first and second solutionsrespectively and mixing the first and second solutions into a mixture.The system further includes a substrate stage for holding a substrateand a supply nozzle coupled to the third supply pipe for dispensing themixture to the substrate. The system further includes a first controlunit coupled to the first supply pipe and configured to control a flowrate of the first solution going to the third supply pipe. The systemfurther includes a second control unit coupled to the second supply pipeand configured to control a flow rate of the second solution going tothe third supply pipe.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for lithography patterning, comprising:forming a first layer over a substrate, the first layer beingradiation-sensitive; exposing the first layer to a radiation; mixing afirst solution and a second solution, thereby forming a developer; anddispensing the developer to the exposed first layer, resulting in apattern over the substrate, wherein the dispensing of the developerincludes varying a concentration of a developing chemical in thedeveloper in multiple stages, such that the concentration of thedeveloping chemical in the developer increases from a first stage to asubsequent second stage, and increases from the second stage to asubsequent third stage real-time during the dispensing.
 2. The method ofclaim 1, wherein the varying of the concentration includes: flowing thefirst solution containing the developing chemical through a first supplypipe; flowing the second solution through a second supply pipe; mixingthe first and second solutions through a third supply pipe that couplesto both the first and second supply pipes; and adjusting a flow rate ofthe first solution or a flow rate of the second solution, so as to varythe concentration over time, such that the concentration exhibits apeak.
 3. The method of claim 2, wherein the peak of the concentration isachieved at the third stage before the concentration decreases from thethird stage to a subsequent fourth stage.
 4. The method of claim 2,wherein the third supply pipe includes a tank for the mixing of thefirst and second solutions.
 5. The method of claim 4, wherein the tankis larger in diameter than a section of the third supply pipe away fromthe tank.
 6. The method of claim 1, wherein the first solution includesa positive tone developer and the second solution is deionized water(DIW).
 7. The method of claim 1, wherein the first solution includes anegative tone developer and the second solution includes an organicsolvent.
 8. The method of claim 1, wherein the dispensing of thedeveloper includes flowing the developer through a nozzle that ismovable above the substrate.
 9. The method of claim 1, wherein the firstsolution contains the developing chemical at a first concentration andthe second solution contains the developing chemical at a secondconcentration that is larger than zero and different from the firstconcentration.
 10. A method for lithography patterning, comprising:providing a substrate; forming a first layer over the substrate, thefirst layer being radiation-sensitive; exposing the first layer to aradiation; dispensing a developer from a first nozzle onto the firstlayer to result in a pattern over the substrate, wherein the developerincludes a developing chemical; dispensing a surfactant-containingtreatment chemical from a second nozzle to the first layer, wherein aconcentration of the surfactant-containing treatment chemical isadjustable; and dispensing a deionized water from a third nozzle to thefirst layer.
 11. The method of claim 10, wherein the concentration ofthe surfactant-containing treatment chemical is adjustable real-timeduring the dispensing of the surfactant-containing treatment chemical.12. The method of claim 10, wherein each of the first, second, and thirdnozzles is independently movable with respect to the substrate.
 13. Themethod of claim 10, wherein the developer has a concentration thatvaries over time during the dispensing such that the concentrationincreases continuously to a peak and decreases continuously after thepeak.
 14. The method of claim 10, wherein the developer has aconcentration that varies over time during the dispensing such that theconcentration increases monotonously to a peak through a first pluralityof consecutive stages and decreases monotonously after the peak in asecond plurality of consecutive stages.
 15. The method of claim 10,further comprising: after the dispensing of the surfactant-containingtreatment chemical, treating the first layer with anothersurfactant-containing treatment chemical, wherein thesurfactant-containing treatment chemical and the anothersurfactant-containing treatment chemical include different surfactants.16. A method for lithography patterning, comprising: providing asubstrate; forming a first layer over the substrate, the first layerbeing radiation-sensitive; exposing the first layer to a radiation; andapplying a developer onto the exposed first layer to result in a patternover the substrate, wherein the developer includes a developingchemical, the applying of the developer includes multiple stages, aconcentration of the developing chemical in the developer increases fromone stage to a subsequent stage in at least two consecutive stages in afirst half of the multiple stages, and decreases from one stage to asubsequent stage in at least two consecutive stages in a second half ofthe multiple stages that is after the first half of the multiple stages.17. The method of claim 16, wherein the applying of the developerincludes dispensing the developer from a supply pipe to the exposedfirst layer; and further includes: supplying a first solution containingthe developing chemical through a first input pipe to the supply pipe ata first flow rate; supplying a second solution through a second inputpipe to the supply pipe at a second flow rate, wherein the first andsecond solutions mix in the supply pipe to form the developer; andadjusting at least one of: the first flow rate and the second flow rate.18. The method of claim 17, wherein the second solution contains thedeveloping chemical at a lower concentration than the first solution.19. The method of claim 17, wherein the second solution is a solventfree of the developing chemical.
 20. The method of claim 16, wherein theat least two consecutive stages in the first half of the multiple stagesinclude first three stages of the multiple stages and the at least twoconsecutive stages in the second half of the multiple stages includelast three stages of the multiple stages.